Patent trolls can stymie innovation and bring otherwise successful companies to their knees. They’re also crazy, as John Oliver points out in this clip from Last Week Tonight.

Patents remain a vital means for inventors to protect their ideas—but trolling can be lucrative, especially in software. Sat on enough of the things, a troll can threaten a company with legal action if it doesn’t pay to license a dubious patent. Large companies, too, can hinder the success of small businesses by charging them huge sums to license patents that cover very simple ideas. Either way, the result is often the same: it’s harder to innovate because someone wants to make some money. John Oliver thinks the whole thing is crazy. He’s right. [ YouTube]

Note: Those of you outside the U.S. may have to watch the video through nefarious means,